Reportable Operating Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Selected business segment financial information
Net interest income (expense)	$ 162,736	$ 132,593	$ 441,755	$ 393,232
Benefit (Provision) for credit losses	(3,183)	4,000	1,564	39,000
Net interest income after provision for credit losses	159,553	136,593	443,319	432,232
Noninterest income	45,857	50,104	131,374	143,343
Noninterest expense	(113,332)	(101,036)	(326,549)	(296,730)
Income before provision for income taxes	92,078	85,661	248,144	278,845
(Provision) benefit for income taxes	(23,060)	(21,382)	(62,047)	(70,132)
Net income	69,018	64,279	186,097	208,713
Total assets	24,870,272		24,870,272		$ 24,992,410
Retail Banking
Selected business segment financial information
Net interest income (expense)	117,060	97,547	318,476	289,107
Benefit (Provision) for credit losses	(773)	3,067	682	17,191
Net interest income after provision for credit losses	116,287	100,614	319,158	306,298
Noninterest income	24,480	22,698	70,280	68,768
Noninterest expense	(76,820)	(60,870)	(220,397)	(185,874)
Income before provision for income taxes	63,947	62,442	169,041	189,192
(Provision) benefit for income taxes	(16,093)	(15,660)	(42,139)	(47,670)
Net income	47,854	46,782	126,902	141,522
Commercial Banking
Selected business segment financial information
Net interest income (expense)	39,586	41,218	111,500	119,718
Benefit (Provision) for credit losses	(1,227)	4,233	701	23,728
Net interest income after provision for credit losses	38,359	45,451	112,201	143,446
Noninterest income	19,848	18,317	58,918	53,886
Noninterest expense	(28,079)	(26,371)	(81,546)	(73,842)
Income before provision for income taxes	30,128	37,397	89,573	123,490
(Provision) benefit for income taxes	(7,458)	(9,269)	(21,962)	(30,898)
Net income	22,670	28,128	67,611	92,592
Treasury and Other
Selected business segment financial information
Net interest income (expense)	6,090	(6,172)	11,779	(15,593)
Benefit (Provision) for credit losses	(1,183)	(3,300)	181	(1,919)
Net interest income after provision for credit losses	4,907	(9,472)	11,960	(17,512)
Noninterest income	1,529	9,089	2,176	20,689
Noninterest expense	(8,433)	(13,795)	(24,606)	(37,014)
Income before provision for income taxes	(1,997)	(14,178)	(10,470)	(33,837)
(Provision) benefit for income taxes	491	3,547	2,054	8,436
Net income	$ (1,506)	$ (10,631)	$ (8,416)	$ (25,401)